Field of the Invention
The present invention relates generally to actuators, and more particularly, to fluid-powered rotary actuators in which axial movement of a piston results in relative rotational movement between a body and a shaft.
Description of the Related Art
Rotary helical splined actuators have been employed in the past to achieve the advantage of high-torque output from a simple linear piston-and-cylinder drive arrangement. The actuator typically uses a cylindrical body with an elongated rotary shaft extending coaxially within the body, with an end portion of the shaft typically providing rotational output drive and the body held stationary, although in some applications the rotational output drive may be provided by the body with the shaft held stationary. An elongated annular piston sleeve has a sleeve portion splined to cooperate with corresponding splines on the inward wall of the body sidewall and on the outward wall of the shaft. The splines may be formed directly on the inward wall of the body sidewall or one a ring gear formed on or connected to the body sidewall. The piston sleeve is reciprocally mounted within the body and has a piston head portion for the application of fluid pressure to one or the other opposing sides thereof to produce axial movement of the piston sleeve.
As the piston sleeve linearly reciprocates in an axial direction within the body, outer helical splines of the sleeve portion engage helical splines on the inward wall of the body sidewall to cause rotation of the sleeve portion. The resulting linear and rotational movement of the sleeve portion is transmitted through inner helical splines of the sleeve portion to helical splines on the outward wall of the shaft to cause the shaft to rotate relative to the body. Bearings are typically supplied to rotatably support one or both ends of the shaft relative to the body.
Reducing the length and weight of fluid-powered rotary actuators and increasing their durability are an almost always present challenge. As is reducing the cost of the actuator.
It will be therefore be appreciated that there has long been a significant need for fluid-powered actuators that have a reduced length and are lighter in weight, and are less expensive to manufacture. The present invention fulfills these needs and further provides other related advantages.